BadTerm

The badass terminal.

A cross-platform ANSI-BBS client (telnet, SSH and RLogin) written in Rust, in the tradition of SyncTERM, NetRunner and mTelnet. Runs natively on Windows, macOS and Linux.

BadTerm draws its own text-mode screen using real CP437 bitmap fonts, so ANSI art renders pixel-for-pixel as it did on a VGA card. It doesn't depend on the fonts and colors of a host terminal.

BadTerm was called Phosphor up to version 0.1.16. Its dialing directory, settings, themes, bezels and saved passwords move over the first time BadTerm starts.

Status: early development (0.1). Telnet, telnet over TLS, SSH, RLogin and raw TCP connections, ZMODEM file transfers, ANSI-BBS emulation, iCE colors, scrollback, capture and the dialing directory with import/export work. See ROADMAP.md for what's planned.

Features

• ANSI-BBS emulation: cursor movement, erase/insert/delete, scroll regions, save/restore cursor, cursor position reports (used by BBSes to detect ANSI), CP437 "graphic" control characters, form feed clears the screen
• Fonts: the IBM VGA fonts, and the Amiga fonts (Topaz, Topaz Plus, MicroKnight, MicroKnight Plus, P0T-NOoDLE, mO'sOul) for Amiga BBSes: set per directory entry, or by the BBS with CTerm's font selection (CSI n ; m SP D, including the bright and blink font slots of CSI ?31h / ?34h)
• Palette changes from the BBS (OSC 4, reset with OSC 104), as SyncTERM does
• Colors: 16-color VGA palette with bold-as-bright, iCE colors (blink bit selects a bright background; toggle with Alt-I, or by the server with CSI ?33h), real blinking text when iCE is off, xterm 256-color, and 24-bit color (SGR 38;2 and the CTerm/PabloDraw CSI 1;r;g;b t form)
• Telnet with BINARY, ECHO, SGA, TERMINAL-TYPE and NAWS negotiation; telnet over TLS ("TelnetS", port 992); RLogin, which logs straight in with the entry's user name and password; raw TCP for systems that don't speak telnet
• SSH (pure Rust, no OpenSSL): "none" auth for BBSes that run their own login, public keys (a key file set in the entry, your SSH agent, or ~/.ssh/id_ed25519, id_ecdsa, id_rsa), keyboard-interactive and password auth. Anything not stored, such as a password, a key passphrase or a one-time code, is asked for in a login dialog. Host keys are trusted on first use and pinned in BadTerm's own known_hosts; a changed key is refused with an explanation.
• ZMODEM downloads start automatically when the BBS sends a file. Uploads start with Alt-U, by dropping files on the window, or automatically when the BBS starts receiving. Batches, progress, speed and ETA are shown, and Esc cancels. Downloads never overwrite existing files. An interrupted download is kept as name.part and resumes where it stopped when the BBS sends the file again (ZMODEM crash recovery).
• YMODEM, YMODEM-G and XMODEM (CRC, 1K or the original checksum), for BBSes and doors that offer them: start the BBS's side, then Alt-G to download or Alt-U to upload. YMODEM keeps file names and sizes and sends several files; XMODEM asks what to save a download as.
• A file picker for uploads: browse folders, mark several files with Space, or press Tab to type a path
• An ANSI viewer (Alt-F, badterm file.ans, or drop a file on the window when not in a call): scroll through art in its own width, font and colors, with its SAUCE title, artist, group, date and comments (I)
• CP437 and UTF-8 sessions, switchable per entry or live with Alt-E
• Commodore 64 (PETSCII) and Atari 8-bit (ATASCII) BBSes, set by the entry's encoding: their 40-column screens, colors, character sets (the C64's two, switched by the BBS), reverse video and screen-editor codes, and their keys (Enter, DEL, the cursor keys, the C64's F1 to F8 and RUN/STOP on Esc). The fonts are BadTerm's own, in those machines' style
• Scrollback of 10,000 lines. Screens cleared by the BBS are kept, so you can scroll back through menus you've already left.
• Session capture to .ans files (Alt-C)
• Copy with the mouse: drag to select text and it is copied when you let go; hold Shift as you let go to copy it with its colors, as ANSI
• Save the scrollback (Alt-S) as an .ans file for ANSI viewers and editors, or as plain .txt, or save the screen as a .png
• Dialing directory with add/edit/delete, quick connect, call counts, last-called dates, pinned favorites, search (/), and sorting by name, last called or number of calls (S). It starts with The Vortex BBS, the project's home BBS.
• Passwords in the OS keychain (Keychain on macOS, Credential Manager on Windows, the Secret Service on Linux) rather than the directory file. Where no keychain is available, they stay in the file.
• Import/export of SyncTERM .lst, CSV, JSON and TOML directories. Use the dialer, the command line, or drag a file onto the window.
• ANSI music: BBS tunes in the BASIC PLAY language (ESC [ N or ESC [ | up to Ctrl-N) play as PC-speaker square waves. Alt-M turns it off, or also on for ESC [ M, which many doors use but which otherwise means "delete a line"
• Phosphor mode (Alt-P): the look of a CRT, with glowing text, scanlines and curved glass, in color or as a green or amber monochrome monitor, for every BBS or chosen per directory entry. BadTerm starts in it: a color CRT with medium scanlines and flat glass, 8-dot characters and square pixels, fitted to the window in its own shape
• VGA-accurate display options: 9-dot character cells, where the line-drawing characters join up as they did on a VGA (Alt-W), and the 4:3 shape of a CRT instead of square pixels (Alt-A). Entries can use 80x43, 80x50 and 132-column screen modes.
• Baud rate emulation, per entry (300 to 115200 bps): text arrives at the speed it was drawn for, so ANSI animations play as intended. ZMODEM transfers still run at full speed.
• Clipboard paste. A normal window scales by whole numbers so every pixel is exact; fullscreen (Alt-Enter) and maximized windows fill the screen, keeping the shape and keeping the pixels sharp.

Installing

Downloads are on the website and the releases page.

• Windows: run badterm-…-windows-x64-setup.exe. It installs for you alone without administrator rights (or for everyone, if you choose), adds BadTerm to the Start menu and opens telnet://, telnets:// and rlogin:// links with it. Or unzip badterm-…-windows-x64.zip and run badterm.exe from anywhere.
• macOS: open badterm-…-macos-arm64.dmg and drag BadTerm to Applications. BadTerm isn't signed with an Apple Developer ID yet, so the first time, Control-click it and choose Open. It opens telnet:// links once it has been run.
• Linux: install badterm-…-linux-x64.deb (Debian, Ubuntu) or badterm-…-linux-x64.rpm (Fedora, RHEL, openSUSE), for example with sudo apt install ./badterm-…-linux-x64.deb. They, the AppImage and the tarball need glibc 2.28 or newer: Debian 10, Ubuntu 20.04, RHEL 8 and later. Or use the AppImage, which runs on most distributions: chmod +x it and run it. The tarball has the bare program, plus badterm.desktop and badterm.png for adding it to your menus by hand (copy them to ~/.local/share/applications/ and ~/.local/share/icons/hicolor/256x256/apps/).

Building

Install Rust (stable, 1.89 or newer) from https://rustup.rs, then:

cargo build --release
./target/release/badterm

No extra system libraries are required on Linux: X11 and Wayland are both supported, and they and ALSA (for ANSI music) are loaded at run time.

Usage

BadTerm opens with its splash screen for two seconds (any key skips it; Settings, General turns it off), then a start-up banner with the version, as terminal programs did.

badterm                         start, not connected (Alt-D opens the dialing directory)
badterm bbs.example.org         connect directly (also host:port,
                                 telnet://host:port, telnets://host:port,
                                 rlogin://user@host, raw://host:port,
                                 ssh://user@host:port)
badterm --import syncterm.lst   add entries from a SyncTERM, NetRunner (.phn),
                                 MagiTerm or EtherTerm directory, a CSV list (ours, or the Telnet BBS
                                 Guide's bbslist.csv), JSON or TOML
badterm --export bbses.csv      write the directory (format from extension)
badterm --paths                 show where data is stored
badterm --render art.ans out.png
                                 draw an ANSI file to a PNG (add --screen for
                                 just the last 80x25 screen, --crt color|green|
                                 amber, --nine-dot, --aspect)

On Windows, BadTerm is a GUI program, so cmd doesn't wait for it and its command-line output can appear after the next prompt. Use start /wait badterm --help in cmd, or run it from PowerShell.

Dialing directory keys

Open the dialing directory with Alt-D (Cmd-D on macOS) at any time. If you are connected, the call stays up behind it, and dialing another BBS asks before hanging up.

Key	Action
Enter	Dial the selected entry
Ins / A	Add an entry
E / F2	Edit the selected entry
Del / D	Remove the selected entry
P	Pin or unpin the entry (pinned entries are listed first)
/, F3, Ctrl-F	Search by name, address or comment (Enter dials, Esc clears)
S	Sort by name, last called, or number of calls
Q	Quick connect to an address
I / X	Import / export a directory file
letter or digit	Jump to the next entry starting with it
Esc	Close the dialing directory

Hotkeys

Every client command is on Alt (on macOS, Cmd, since Option types characters there). Every Ctrl key, Ctrl-D included, always goes to the BBS.

Key	Action
Alt-D	Open or close the dialing directory
Alt-H	Hang up (or clear a finished call from the screen)
Alt-R	Call again (after a hang-up, or now while a redial is waiting)
Alt-L	Send the entry's user name; again for the password
Alt-1 ... Alt-0	Keyboard macros (set them in Settings, Alt-O)
Alt-B, Shift-PgUp, mouse wheel	Scrollback (arrows, PgUp/PgDn, Home; any other key returns)
Alt-I	Toggle iCE colors / blinking
Alt-E	Toggle CP437 / UTF-8
Alt-C	Start/stop capturing to a file
Alt-S	Save the scrollback (.ans, .txt) or the screen (.png)
drag with the mouse	Copy the selected text (Shift on release: as ANSI)
Alt-U	Upload files: ZMODEM, YMODEM or XMODEM (or drop files on the window)
Alt-G	Download with YMODEM or XMODEM (ZMODEM downloads start by themselves)
Alt-V, Shift-Ins	Paste from the clipboard
Alt-Enter	Toggle fullscreen (fills the screen, keeping the shape)
Alt-P	Phosphor mode: off, color CRT, green screen, amber screen
Alt-A	Aspect ratio: square pixels, 4:3 as on a CRT, 16:10, 16:9
Alt-W	9-dot or 8-dot character cells
Alt-M	ANSI music: on, on including ESC [ M, off
Alt-O	Settings, and the interface colors
Alt-F	View ANSI art: a file picker, then the art with its SAUCE details
Alt-Z	Help: every key on one page
Alt-X	Exit (asks first; Y or Alt-X again to confirm)

Alt-P, Alt-A, Alt-W and Alt-M work anywhere, including in the dialing directory, and are remembered in settings.toml. An entry's "Screen mode" can be 80x25, 80x43, 80x50, 132x25, 132x37 or 132x52 (43 lines or more in the 8x8 font), and its "Phosphor mode" can override Alt-P for that BBS. While connected to a BBS with its own phosphor mode, Alt-P changes that BBS's mode rather than the global one. Its "iCE colors" setting is Auto (the BBS turns them on with CSI ?33h, as before), On or Off; with On or Off, Alt-I changes that BBS's setting too.

Alt-O (or O in the dialing directory) opens the settings, on four tabs (Tab and Shift-Tab, or PgUp/PgDn, move between them). Folders sets where downloads, captures and saved screens go and where the upload and ANSI-art pickers start (Enter to change, Del for the default). The others: phosphor mode, its scanlines (off, light, medium or strong) and the curve of its glass (off for a flat screen, slight, medium or strong), the aspect ratio, scaling (fit keeping the shape; auto, which is whole numbers in a window and fit in full screen; always whole numbers; or stretch to fill), character cells, ANSI music, redialing, and the colors of BadTerm's own screens. Pick one of the color schemes (Midnight, the default; Classic blue, Gray windows, Green phosphor, Amber, Monochrome), or, under "Edit colors", give each part of the interface (title bar, selected entry, windows, input fields, key hints, ...) its own foreground and background from a grid of the 16 x 8 combinations, as in QModem and Telix. Changes show and are saved straight away; in the grid, Esc undoes the last part.

"Keyboard macros" sets what Alt-1 to Alt-0 send, written as in Telix and QModem: ^M is Enter, ^[ Esc and ^A to ^Z the other control keys, ~ waits half a second, and {user} and {password} are the directory entry's. {user}^M~{password}^M, for example, logs in.

Color themes can be shared. "Save as a theme" writes the current colors to a file in the themes folder (badterm --paths shows where), and "Import a theme" copies someone else's file there and switches to it. Every theme in the folder is in the color scheme list. A theme is a small TOML file, easy to edit by hand; parts it leaves out keep the default colors:

name = "Sunrise"
author = "sysop"

[colors]
title_bar = { fg = "yellow", bg = "red" }
selected = { fg = "black", bg = "brown" }
window = { fg = "white", bg = "magenta" }

The colors are black, blue, green, cyan, red, magenta, brown, light gray, dark gray, light blue, light green, light cyan, light red, light magenta, yellow and white. The parts are title_bar, border, headings, entries, selected, info, help, help_key, status, status_alt, window, window_title, window_text, field_name, field_value, input, keys, note and error.

"Monitor bezel" draws a monitor around the screen: a beige 1980s monitor, a platinum 1990s one, a charcoal late-1990s one, or a terminal (original designs, not any maker's). The picture then fills the monitor's 4:3 screen, as it did on the real thing; it looks best with phosphor mode on. For your own, put a PNG in the bezels folder, with the screen area see-through (transparent): BadTerm finds the screen from the transparent part in the middle and draws the terminal there. A photo of your own old monitor works well.

"Check for updates" is off unless you turn it on. When it is on, BadTerm asks git.badcluster.dev for the newest release once each time it starts (one HTTPS request, with nothing in it but BadTerm's version), and if there is a newer one says so on the status bar and the start screen, with a link to the website. It never downloads or installs anything itself.

Downloads are saved to Downloads/BadTerm; badterm --paths shows every location BadTerm uses.

For SSH entries, set the user name in the entry. Many BBSes accept a user like new or guest and then run their own login. BadTerm logs in with:

1. "none", which is all most BBSes need;
2. public keys: the entry's "SSH key file" (asking for its passphrase if it has one), then your SSH agent (SSH_AUTH_SOCK; on Windows the OpenSSH agent service or Pageant), then unencrypted ~/.ssh/id_ed25519, id_ecdsa and id_rsa. Encrypted default keys are skipped rather than asking for a passphrase on every BBS that offers key logins: add them to your agent, or name one in the entry;
3. keyboard-interactive or password, using the entry's password if there is one and asking otherwise (or when it is refused). The login dialog can remember the password for next time (Tab).

Entries with a user name log in by themselves over telnet (the entry's "Auto-login" setting): once the BBS pauses at a prompt such as Login:, User name: or Synchronet's NN:, BadTerm sends the user name, and then the password at Password:. It answers each once, only in the first two minutes of a call, and never sends the password before the user name. Alt-L sends them by hand instead, one press each.

A BBS that can't be reached, or that answers and hangs up straight away saying it is busy, is called again every 15 seconds, up to 10 times; Esc stops it and Alt-R calls at once. Set redial = false in settings.toml to turn this off.

Telnet over TLS checks the BBS's certificate against the usual certificate authorities. Many BBSes use self-signed certificates, so one that fails that check is trusted on first use and pinned in tls_known_hosts (beside known_hosts), and a later, different certificate is refused; so is a self-signed certificate from a BBS whose certificate an authority signed before.

RLogin sends the entry's password as the "client user name" and its user name as the "server user name", as SyncTERM does, which is how Synchronet and other BBSes log RLogin callers in.

Passwords you enter in the directory, remember from the login dialog, or import with a SyncTERM list are moved into the OS keychain when the directory is saved. Exported directories don't include them.

Keys are sent the way ANSI-BBS software expects: arrows as ESC [ A..D, Home/End as ESC [ H / ESC [ K, PgUp/PgDn as ESC [ V / ESC [ U, Ins as ESC [ @ and Del as DEL.

Website

site/ holds the project's static web page; see site/README.md.

Project layout

crates/badterm-core   front-end independent library: CP437, screen model,
                       ANSI parser, telnet, dialing directory, sessions
crates/badterm        the windowed client (winit + softbuffer), renderer,
                       text-mode dialer UI

badterm-core has no GUI dependencies, so it can drive other front ends (a TUI, a headless bot, a test harness) as well.

Testing

cargo test

The ZMODEM interoperability tests run against lrzsz's sz and rz when they are installed (apt install lrzsz, brew install lrzsz) and are skipped otherwise; CI sets BADTERM_REQUIRE_LRZSZ=1 so they can't be skipped there.

To render sample frames to images for visual inspection:

BADTERM_SNAPSHOT_DIR=/tmp/shots cargo test -p badterm snapshot -- --ignored

License

Copyright (C) 2026 Bad Cluster.

BadTerm is free software, licensed under the GNU General Public License, version 3 or (at your option) any later version. See LICENSE.

The bundled VGA fonts come from DOSBox (GPL-2.0-or-later). See crates/badterm/assets/fonts/README.md.